Single direction cam for insert molding machine

ABSTRACT

An insert molding machine has first and second mold sections, one of which is movable between open and closed positions, A slide carrying inserts is movable from an open position to a closed position wherein the slide and first and second mold sections define a mold cavity in which a part is molded. A single direction cam mechanism in the slide engages a pin in the movable mold section to releasably connect the slide and movable mold section during closure. The connection causes the slide to open upon subsequent opening of the movable mold section but allows the slide to be closed independently of the movable mold section.

BACKGROUND OF THE INVENTION

This invention relates to insert molding machines. Such machines makemolded parts having embedded pieces, called inserts, integrally formedtherein. For example, a part may have metal pieces forming electricalcontacts molded within a plastic switch housing. The inserts aresupported within a mold cavity on a slide prior to introduction of themolten molding material. When the part is cured the inserts, of course,are released from the slide and remain in the part.

The mold cavity is defined by the slide and two or more mold sections.At least one of the mold sections is movable between open and closedpositions. One or more of the mold sections has an aperture whichreceives the slide. The slide is also movable between open and closedpositions. In the open position the slide is retracted from the moldsections to facilitate loading of the inserts thereon. In the closedposition the slide cooperates with the mold sections to define the moldcavity.

It is desirable to mechanically connect the movable mold section andslide so that only a single drive mechanism need be provided to moveboth parts. The mechanical connection between the movable mold sectionand slide causes them to open and close together. That is, opening orclosing movement of a mold section simultaneously causes opening orclosing movement of the slide. This has been done in the past with anangle pin entrapped in a closed slot. In effect, the angle pin andclosed slot form inclined planes on the mold section and slide. Thus,vertical motion of the mold section induces horizontal motion of theslide and the two parts open and close together.

A drawback of this approach to effecting movement of the slide is thatis does not permit inspection of the inserts in their final positions.Since the slide does not reach its fully closed position until themovable mold section also closes, it is not possible with conventionalmachines to verify that all of the inserts are properly located in themold cavity. Sometimes slide movement will displace an insert but thiscannot be seen because the mold cavity is closed when the slide finallygets to its closed position. Misplaced inserts cause defective moldedparts. Hydraulically operated slides have been proposed to solve thisproblem but their introduction increases the complexity of the equipmentand are more trouble than they are worth.

SUMMARY OF THE INVENTION

The present invention relates to insert molding machines and isparticularly directed to a single direction cam mechanism that permitsindependent closing of the slide and movable mold section while causingsimultaneous opening of these elements. Thus, the slide can be closedprior to closing the mold sections. Once the slide is closed, but beforethe mold sections are closed, inspection of the inserts can be made toassure they are properly positioned. Then the mold sections are closedpreparatory to the actual molding operation. Once the part is cured,opening of the mold sections will cause the slide to open as well.

The single direction cam mechanism includes an angle pin connected tothe movable mold section and a slot formed in the slide. The slot isdefined by a throat and two walls on either side of the throat. Oppositethe throat is an open side of the slot. The top of the slot is openalso. Spring-loaded fingers or cams retractably extend across the openside of the slot. When the movable mold section is closed onto thepreviously-closed slide, the angle pin slips into the slot through theopen side. A rounded surface on the leading edge of the angle pinengages a cam face on the cams to retract them and allow passage of theangle pin into the throat of the slot. Once the pin passes the cams, aflat surface on the trailing edge of the angle pin engages the cams andprevents withdrawal of the pin upon subsequent opening of the movablemold section. Engagement of the angle pin and cams causes the slide toopen with opening of the movable mold section. When the movable moldsection gets close to its fully open position the angle pin slips outthe top of the slot, allowing the slide to move independentlythereafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of the slide and stationary mold section with theslide in its open position.

FIG. 2 is a section taken along line 2--2 of FIG. 1 with the slide andthe movable mold section shown in solid lines in their closed positionsand in phantom lines in their open positions.

FIG. 3 is an enlarged plan view of the slide.

FIG. 4 is a section taken along line 4--4 of FIG. 3.

FIG. 5 is a section taken along line 5--5 of FIG. 3.

FIG. 6 is an end elevation view of the slide.

FIG. 7 is an enlarged plan view of a cam.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a first, stationary mold section generally at 10. The moldsection includes a base plate 12 on which guide sleeves 14 and pins 16are mounted to mesh with similar pins and sleeves on a second, movablemold section. A wall 18 extends along one edge of the base plate 12. Asecond wall 20 extends along a portion of the opposite edge of the baseplate 12.

A mold cavity indicated at 22 is defined by the base plate 12 and threeupstanding walls 24, 26, and 28. The walls are joined together to form athree-sided enclosure having an opening or aperture at 30. Walls 24 and26 have a passage 32 for supplying molten mold material to the moldcavity 22.

The walls 18 and 20, together with the base plate 12, define a well inwhich a slide 34 is movable between open and closed positions. The slideis shown in FIG. 1 in its open position wherein it is retracted from theaperture 30. The extent of the slide's retraction is limited by stopscrews 36. The closed position of the slide is defined by the frontfaces 24A and 28A of the walls 24 and 28.

The slide 34 has a main block 38 and an insert block 40 fastened to thefront face of the main block. The front surface of the insert blockholds the inserts, examples of which are shown at 42. The inserts aretypically hand loaded into slots or retainers in the insert block 40.Details of the main block 38 will be described below. The slide 34 isretained in the well by a pair of rails 44 and 46 which are bolted tothe walls 18 and 20 respectively.

Turning now to FIG. 2, the second, movable mold section is showngenerally at 48. The movable mold section reciprocates between a closedposition shown in solid lines and an open position shown in phantomunder the control of a conventional drive mechanism. The movable moldsection closes the top of the mold cavity when in its closed position.As mentioned above, it has pins and sleeves (not shown) engageable withthose of the stationary mold section to guide its movement and maintainalignment of the first and second mold sections.

The movable mold section 48 carries an angle pin 50. The angle pin isgenerally cylindrical except for a flat portion 52. There are two anglepins in this embodiment. The base plate 12 of the stationary moldsection has a clearance opening 54 which receives the angle pin when themold is closed.

Turning now to FIGS. 3-7, details of the slide are shown. The main block38 has ledges 56 on each end. The ledges are engaged by the rails 44 and46 to retain the slide in the well of the stationary mold section. Thefront side of the main block 38 has a depression 58 into which theinsert block 40 fits. It will be understood that the main block 38 alsohas a plurality of cooling water passages which are not shown.

The slide also has slots formed in the back edge of the main block forreceiving the angle pin 50. Two slots are shown in the illustratedembodiment. It will be understood that, depending on the particularapplication, a different number of slots may be used. The slots areidentical and only one will be described in detail. The slots aredefined by two side walls 60, 62, and a throat 64. Opposite the throatis an open side of the slot indicated generally at 68. It will be notedthat the throat 64 is inclined with respect to the vertical, at the sameangle as the angle pin 50.

The main block 38 of the slide has bores or pockets 70A and 70B drilledon each side of the slots. Each pocket 70 opens at one end into theslots and is closed at the other end. The pockets nearest the edges ofthe slide are closed by retainer plates 72 which in turn are fastened tothe main block 38 by bolts 74. The closed end of the pockets receives aspring 76A, 76B. The springs bias a cam or finger 78A, 78B outwardly ofthe pockets 70.

The cams 78 are all alike. Details are shown in FIG. 7. The cams aregenerally cylindrical with a bore 80 in their inner end which receives aspring 76. A groove 82 along one outer surface of the cams receives ananti-rotation screw 83 (FIG. 5) to prevent rotation of the cam in thepockets. Screw 83 fits in a hole 81 (FIG. 4) in the block 38. Cam face84 on the outer end of the cam is directed toward the open end 68 of theslot. Opposite the cam face 84 is a flat portion 86 engageable with theflat 52 on the angle pin, as described below.

The use, operation, and function of the invention are as follows. Withthe movable mold section 48 raised and the slide 34 retracted to theposition of FIG. 1, inserts 42 are hand loaded on the front face of theinsert block 40. The slide is then closed by moving it to the positionof FIG. 2, thereby closing off the aperture 30. With the inserts intheir final position in the mold cavity, inspection can be had to assurethat they are properly located. After inspection of the insert location,the mold is closed by lowering the movable mold section 48. As itdescends the two angle pins 50 slip into the open sides 68 of the slotsof the slide 34. Continued downward motion of the angle pins bringstheir leading, rounded edges into engagement with the cam faces 84causing the cams 78a, 78B to retract into the pockets 70A, 70B. As themovable mold section reaches its fully closed position, the angle pins50 move completely past the cams 78 and settle on or near the throat 64.The cams snap back to their fully extended position under the urging ofthe springs 76 with the flat surfaces 86 of the cams engaging the flats52 of the angle pins.

Once the mold cavity is fully closed, molten mold material (typicallysome type of plastic) is introduced into the mold cavity 22 in asuitable manner, for example through the passage 32. After the moldedpart has cured, the mold is opened by raising the movable mold section48 vertically. When the angle pins start moving upwardly the engagementof the flat surfaces 86 and the flats 52 causes the slide to open withthe movable mold section. The slide moves horizontally as it isprevented from vertical motion by engagement of the rails 44 and 46 withthe ledges 56. Continued upward movement of the movable mold sectioneventually causes the angle pin to slip out of the top of the slot,thereby freeing the slide for subsequent independent movement.

Whereas a preferred form of the invention has been shown and described,it will be realized that alterations may be made thereto withoutdeparting from the scope of the following claims. For example, it is notrequired that the slide be closed prior to the movable mold section. Ifdesired, the slide could be left open when the closure of the movablemold section begins. The angle pins would then slip past the cams asdescribed above, engage the throat 64 and push the slide to the closedposition as the movable mold section closes.

We claim:
 1. An insert molding machine having first and second moldsections at least one of which is movable between open and closedpositions, a slide movable between open and closed positions, the moldsections and slide when in their closed positions cooperating to definea mold cavity in which a part is molded when the mold sections and slideare closed and from which a molded part can be removed when the moldsections are open, and engagement means for releasably connecting theslide to said at least one movable mold section such that the slide andmovable mold section will open simultaneously but are closableindependently.
 2. The structure of claim 1 wherein the engagement meanscomprises a pin extending from one of the movable mold section or slideand a catch formed in the other of the movable mold section or slide,the pin and catch being disposed such that they are engaged ininterfitting relation when both the slide and movable mold section reachtheir closed positions, the pin thereby causing the slide to open withthe movable mold section upon subsequent opening of the movable moldsection, the pin and catch becoming disengaged when the movable moldsection reaches its open position.
 3. The structure of claim 2 whereinthe catch includes at least one slot formed in the slide and at leastone cam retractably extending into the slot.
 4. The structure of claim 3wherein the cam has a cam face arranged to contact the pin entering theslot upon closure of the movable mold section and cause retraction ofthe cam, allowing the pin to move further into the slot and past thecam.
 5. The structure of claim 3 wherein said at least one movable moldsection reciprocates along an axis of motion and the pin and slot aredisposed at an angle to the axis of motion, such that the pin has bothaxial and lateral components of motion and imparts lateral motion to theslide.
 6. The structure of claim 1 wherein at least one of the moldsections defines a mold aperture providing access to the mold cavity,the slide fitting into and closing off the aperture when the slide is inits closed position.
 7. The structure of claim 1 wherein the engagementmeans comprises a pin extending from one of the movable mold section orslide and a catch formed in the other of the movable mold section orslide, the pin and catch being out of engagement when the movable moldsection and slide are in their open positions, the catch permittingrelative movement of the pin past the catch such that they are engagedin interfitting relation when both the slide and movable mold sectionare moved to their closed positions, the catch entrapping the pin uponsubsequent initial opening movement of the movable mold section, therebycausing the slide to open with the movable mold section, the pin andcatch becoming disengaged when the movable mold section reaches itsfully open position.